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Collaborative research from scientists in China, the UK, and the U.S. has shed light on the enigmatic “zombie” volcano, Uturuncu, located in Bolivia. By integrating seismological data, physicochemical models, and rock composition analyses, the team has identified the underlying factors contributing to the volcano’s unusual behavior, alleviating concerns about a potential eruption. This important study has been published in the journal PNAS.
Nestled within the Central Andes, Uturuncu has earned the nickname “zombie” volcano due to its dormant status—having last erupted 250,000 years ago—while still exhibiting signs of volcanic activity such as seismic events and gas emissions. These phenomena are characterized by a distinct “sombrero” deformation pattern, where the land at the volcano’s core rises while surrounding areas sink.
The significance of accurately assessing Uturuncu’s eruptive potential cannot be understated, as an eruption could pose substantial risks to local communities. Previously, the reasons behind the continuous unrest remained elusive, but scientists believed that understanding the movement of magma and gases beneath the surface was crucial.
This comprehensive study utilized expertise from the University of Science and Technology of China, the University of Oxford, and Cornell University. It involved analyzing seismic signals from over 1,700 earthquakes to create a high-resolution image of the volcanic plumbing system located in the shallow crust beneath the volcano.
Findings revealed that the “zombie” characteristics of Uturuncu stem from the movement of liquids and gases beneath the crater, indicating a low probability of an imminent eruption.
Volcanic plumbing systems consist of intricate mixtures of fluids and gases within magmatic reservoirs and hydrothermal systems. It has previously been established that Uturuncu is situated above the Altiplano-Puna Volcanic Complex, which harbors the largest known magma body in the Earth’s crust, and features an active hydrothermal system that connects this magma reservoir to the surface. However, the dynamics of fluid movement within this subsurface system were unclear.
The researchers employed seismic tomography, a technique analogous to medical imaging, to visualize the interior structure of the volcano. Variations in the speed of seismic waves through different materials provided valuable three-dimensional insights into Uturuncu’s internal processes.
Combining seismic imaging with physical property analysis, including rock composition, allowed the team to discern potential pathways for upward migration of heated fluids. This analysis indicated how liquids and gases accumulate in reservoirs beneath the volcano’s crater—a key factor behind the deformation observed.
The research team posits that this fluid behavior is primarily responsible for the deformation patterns and suggests that the risk of a significant eruption remains low.
Co-author Professor Mike Kendall from the University of Oxford remarked on the impact of their findings: “This international collaboration exemplifies how integrating geophysical and geological methodologies enhances our understanding of volcanoes and the associated hazards and resources.”
Co-author Professor Haijiang Zhang from the University of Science and Technology of China emphasized the unique insights gained through the team’s diverse expertise, which facilitated the integration of advanced imaging techniques and modeling of rock properties and fluid interactions.
Professor Matthew Pritchard from Cornell University noted the broader implications of their research: “The methods applied in this study could be extended to over 1,400 potentially active volcanoes, including many that, like Uturuncu, show signs of life despite not being classified as active. These ‘zombie’ volcanoes could benefit from similar analytical approaches.”
The research team expresses optimism that future studies employing this dual analysis of seismic and petrophysical characteristics will deepen understanding of other volcanic systems.
More information: Zhang, Haijiang et al, Anatomy of the magmatic–hydrothermal system beneath Uturuncu volcano, Bolivia, through joint seismological and petrophysical analysis, Proceedings of the National Academy of Sciences (2025). DOI: 10.1073/pnas.2420996122.
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phys.org